The invention relates to a two-part digital electronic indicator arrangement for taximeters of the type adapted to separately display the fare and extra charges.
Usually, taximeters are provided with two viewing windows. The digits indicating the taxi fare are visible through one of the windows, whereas the digits indicating the extra charges, if any, incurred during the trip are visible through the other of the windows. With conventional mechanical or electromechanical taximeters, larger digits were employed for the display of the taxi fare than for the display of the extra charges, in consideration of the fact that the fare is in general of greater interest to the passenger than is the amount of the extra charges. Accordingly, the digits indicating the amount of extra charges are usually relegated to digit-rolls, or the like, bearing smaller digits.
Particularly because the taximeter industry is turning more and more to electrical and electronic taximeters, increasing use is being made of electrical and electronic taximeter indicator arrangements for the taxi fare and for the amount of the extra charges. Additionally, the latter types of taximeter indicator arrangements have the advantage that they are highly visible in the dark, i.e., during trips at night, without, however, incurring the risk that the taxi driver may be momentarily blinded to some extent if he glances at the taximeter.
Electronic illuminated-digit tubes have been known for some time. With one known type, the numerals from "0" to "9" are arranged in one digit zone, one behind the other. This has the disadvantage that when the different numerals in one tube successively light up they appear at different distances from the viewing window, which can detract from the readability of the display, in addition to rendering non-uniform the appearance of a plurality of different numerals being simultaneously displayed using a plurality of illuminated-digit tubes for the display of a multi-digit number.
More recently, so-called 7-segment indicator tubes have been developed. These tubes are each comprised of seven segments so arranged that when all are simultaneously illuminated a rectangular figure "8" is formed. The other numerals are formed by simultaneously illuminating different combinations of the seven segments. This type of tube has the advantage that all the numerals which are displayed will appear at the same distance from the viewing window, i.e., in a fixed plane. However, a problem was involved in the display of multi-digit numbers. The only way to effect this display was to use a corresponding plurality of 7-segment indicator tubes. This is expensive.
Still more recently, cold-cathode gas-discharge indicator tubes have become common. With these, there are arranged in a single such tube a plurality of 7-segment display units arranged fixedly one next to the other. With these new multi-digit-zone iluminated-digit tubes, costs have been reduced, because only a single logical driving circuit is required for one multi-digit-zone tube.
However, these multi-digit-zone illuminated-digit tubes have not proved particularly advantageous for use in taximeter indicator arrangements. One problem is that all the 7-segment digit zones are of the same size, whereas for the reasons explained above it is preferred with taximeters to display different multi-digit numbers using digits of different size. Alternatively, if use is made of two separate multi-digit-zone illuminated-digit tubes, one for the display of one multi-digit number such as the taxi fare, the other for the display of the other multi-digit number such as the amount of the extra charges, then there arises the problem of driving two separate digit tube devices.